Heat Pipe Solar Receiver for Oxygen Production of Lunar Regolith

Abstract

A heat pipe solar receiver operating in the 1050°C range is proposed for use in the hydrogen reduction process for the extraction of oxygen from the lunar soil. The heat pipe solar receiver is designed to accept, isothermalize and transfer solar thermal energy to reactors for oxygen production. This increases the available area for heat transfer, and increases throughput and efficiency. The heat pipe uses sodium as the working fluid, and Haynes 230 as the heat pipe envelope material. Initial design requirements have been established for the heat pipe solar receiver design based on information from the NASA In-Situ Resource Utilization (ISRU) program. Multiple heat pipe solar receiver designs were evaluated based on thermal performance, temperature uniformity, and integration with the solar concentrator and the regolith reactor(s). Two designs were selected based on these criteria: an annular heat pipe contained within the regolith reactor and an annular heat pipe with a remote location for the reactor. Additional design concepts have been developed that would use a single concentrator with a single solar receiver to supply and regulate power to multiple reactors. These designs use variable conductance or pressure controlled heat pipes for passive power distribution management between reactors. Following the design study, a demonstration heat pipe solar receiver was fabricated and tested. Test results demonstrated near uniform temperature on the outer surface of the pipe, which will ultimately be in contact with the regolith reactor.

Thermal Energy Process Heat for Lunar ISRU: Technical Challenges and Technology Opportunities

“…Models of regolith heating cycles require that the regolith be heated by stationary spots for 2.5 hours before the regolith has been effectively processed. 37 Reactor assemblies being used for research and production are too large to move with the progressing spot, so in most cases, the energy needs to be transferred to the stationary reactor. As such, there are multiple ideas for energy transport.…”

“…28. 37 In such a process, incident solar radiation would be focused onto a heat pipe. By using solar energy to evaporate and condense the working fluid within the heat pipe, the heat pipe would transfer heat to the regolith.…”